In a background art, in building steps of fabricating a tire, there is known a building method of building a carcass band in a shape of a circular cylinder as a tire constituting member by adhering and laminating a carcass ply constituting a reinforcement member including, for example, an inner liner, a rubber chafer and a cord comprising a rubber material on a peripheral face of a building drum, building a bead or a side wall on a first stage building drum to constitute a green case, successively, transferring the green case to a second stage drum capable of carrying out a shaping deformation for second stage building, deforming the green case in a toroidal shape (shaping deformation), and building a green tire by adhering a belt, a tread rubber and the like thereon.
In recent years, there is also proposed a method of building a green tire by laminating and building a belt and a tread rubber to be laminated on a carcass band in a shape of a circular cylinder by a separate step and combining the belt/tread band and the carcass band on the second stage building drum. Further, it is also proposed to build a side wall on the second stage building drum.
Meanwhile, a building drum for the second stage building including the shaping deformation is constituted by including a pair of left and right drum portions having bead lock means for holding both side bead portions of a green case constituting an intermediate build member of a tire respectively in a lock state, the two drum portions are provided along a drum shaft to be able to be proximate to and distant from each other in an axial direction, in the shaping deformation, the two drum portions including the bead lock means are moved in directions of being proximate to each other, further, after detaching the built green tire, the two drum portions are constituted to move in directions of being distant from each other.
Normally, as exemplified in Reference 1 shown below, the drum shaft of the building drum constitutes a double shaft structure of an outer side shaft portion in a shape of a cylinder for rotating the two drum portions, and a screw 5 shaft rotatably inserted to inside of the outer side shaft portion and formed with screw portions in directions reverse to each other at left and right portions in the axial direction, the two drum portions are connected to moving members fitted to the outer side shaft portion unrotatably and movably in the axial direction relative thereto and screwed to respective screw portions of the left and right portions of the screw shaft, and the two drum portions are constituted to move to be proximate to and distant from each other along with the bead lock means by screw feeding operation of the screw portions with rotation of the screw shaft.
Further, also in a band building drum which is a drum of building a carcass band and a belt band and in which a drum main body is constituted by segments divided into a plurality thereof in a peripheral direction, as exemplified in Reference 2 shown below, there is known a mechanism of constituting a drum shaft by a double shaft structure of an outer side shaft portion in a shape of a cylinder and a screw shaft at inside thereof and operating to expand and contract the respective segments by moving the moving member in the axial direction by rotating the screw shaft.    Patent Reference 1: U.S. Pat. No. 3,971,694 specification    Patent Reference 2: JP-A-2003-89158